It has long been a practice to control a 110-volt electrical outlet or set of outlets from multiple, usually two, spaced switches, for example, switches being at the bottom and top of stairs between floors of a building by which illumination can readily be controlled at the two levels. This is termed three-way (two switches) switching.
Applicant is aware of two general types of connective systems to effect the necessary connections, one being the widely used, and thus conventional, system of making each desired connection by twisting wires together and covering them with a wire nut. The other type system is one which employs what is termed a modular connector. The applicant found reference to such modulator connectors only in the patent art, as exemplified by U.S. Pat. Nos. 4,820,197, issued Apr. 11, 1989, and 4,875,871, issued Oct. 24, 1989. It is believed that by virtue of their cost and complexity, applicant has not, now more than four years latter, found them available to the electrical trade. They simply have not been found to be a viable option for the wiring of buildings which, of course, is the field to which the present invention is directed.
Conventionally, to effect three-way switching, at least four power cables are connected in an electrical junction box, one bringing power in, a second cable extending to and connected to one switch, a third cable extending to and connected to a second switch, and a fourth cable bringing power out to a light or lights. Sometimes where there are two lights, the lights are separately connected by a cables to the junction box, thus requiring that five cables be interconnected. Further, where, as is often the case, it is desired to extend unswitched conductors, as to a wall outlet, a sixth cable is interconductor connected in the junction box.
Significantly, each of the cables has three conductors, and as a first step, each cable is passed through a cable opening in the junction box. Then each is pulled outward from the interior of the junction box with the top (or bottom) cover of it removed. Next, the ends of the conductors are stripped of insulation. After this, particular conductors are twisted together and wire nuts semi-screwed (there are no male threads) on. Next, the conductors are stuffed back into the junction box. Finally, the cover is replaced on the junction box, making it a full enclosure. Such junction boxes, square or round, typically have a side-to-side dimension of only four inches or less, making the stuffing event difficult, and worse, frequently the stuffing applies forces to the twisted joints which loosens them.
U.S. Pat. No. 4,106,835, issued on Aug. 15, 1978, outlines in part this procedure and discusses certain of the problems encountered with it, with which the applicant concurs:
"In practice, electrical wires are connected by the use of electrical wire nuts. The connected wires and the attached wire nuts are then crammed into a junction box. Wire nuts must be of a size to receive therein the end portions of the number of the wires to be connected together and frequently at least three wires require connection. Wire nuts are of a size to cause the local connection to have considerable bulk. There is also the element of costly time involved in connecting the end portions of wires or in changing connections, and difficulty is frequently experienced in initially connecting wires or in removing the same from a junction box for changing connections." PA1 1. that the device be readily placeable in a standard electrical junction box; PA1 2. that the degree, compression, or inter-element force between connected elements be positively controllable by the installer to enable him to ensure that a low ohmic connection is made by the device; PA1 3. that the device be connectable while positioned in a junction box without the necessity for its removal or the removal of connecting wires; PA1 4. that it accommodate a power input circuit, single or multiple switching functions, a switch controlled output, and preferably a bridging, non-switched output; PA1 5. that when installed, it be configured to enable a simple visual inspection whereby the installer may be certain that all connections are good ones and thus not likely to heat. One cannot see through a wire nut; and if removed for inspection and then replaced, some change in the position of the connected wires is to be expected. Thus, what you see is not necessarily a condition of the wires after replacement of the wire nut; and PA1 6. that it be uniquely configured to facilitate both its functionality and the wiring of it.
It is significant that the employment of wire nuts, which goes back to a day prior to the '835 patent, supplanted taping of the twisted joints with an insulating tape. The basic role of the tape was to provide insulation and thus prevent shorting between wiring connections within the electrical box. The problem asserted with respect to the insulating tape was that following the stuffing event, an imperfect connection might occur or persist within the tape and, of course, unseen, could result in heat, burn, and thus present a significant fire hazard. As a result, wire nuts were adopted, these having an outer plastic or Bakelite.TM. construction, these performing both an insulation function and effecting some securing function to lessen the probability of loosening of twisted wires by stuffing. Further, wire nuts were claimed to be less likely to deteriorate or be destroyed in the presence of heat.
Despite the better insulation feature of wire nuts and the fact that their rigidity would seem to be protective of the integrity of a twisted wire joint they encased and prevent "hot" joints, they remained suspect and unpopular. This is believed to be in part because while the term "nut" suggested a secure fitting, in fact, there was no such security as there typically occurs slippage between twisted wires and the minimum threads of a wire nut.
This is not to say that substitutes for wire nuts have not been suggested by the prior art, particularly in the literature. Thus, the '835 patent describes a terminal block which could be used to provide, positive, bolt secured interconnections as are commonly employed in certain switch boxes and circuit breakers to prevent "hot" joints. Other U.S. Pat. Nos., e.g., 1,668,111; 2,411,014; 3,546,364; and 4,547,627 offer other forms of positive connection terminal blocks.
The problem with known proposed terminal blocks is that they do not meet the clear and, applicant believes, absolute requirement demanded by the trade of providing a universal interconnection device which is simple and inexpensive to use and one that meets a high percentage of wiring installer's needs. It is submitted that the following features are needed in a device to produce an acceptable departure from the prior art:
It is the objective of this invention to address the problems created by the absence of combinations of the foregoing features.
A second problem relating to the wiring of buildings is that of the typical requirement that skilled electricians must make two visits to a job site, once to effect wiring at electrical boxes, and again to connect switches, wall receptacles, and light fixtures. Ideally, the second visit would be eliminated if the latter chores were performable by non-skilled workers, who are paid on the order of one-third that of skilled electricians.
Accordingly, another object of this invention is to overcome this last problem.